1. Field of the Invention
The present invention relates to rafter squares used to determine and mark the correct base cut and common cut angles for rafters and more particularly to a rafter square having a selectively extendable arm that is used to extend the marking edge of the rafter square to accommodate a user in common instances where the marking edge of the rafter square does not extend from one edge of the rafter to the opposite edge of the rafter.
2. Description of the Prior Art
Framers in the construction arts have used rafter squares for many years for determining and marking the correct base cut and common cut angles for rafters and the like. The common rafter square is provided in the form of a right-triangular plate having a flanged base leg, a side leg and a hypotenuse leg. When used for base cut marks, the rafter square is positioned on a board, with its pivot point positioned closely adjacent one edge of the board. The rafter square is pivoted until the appropriate unit rise mark, within a marking orifice formed within the rafter square, is positioned closely adjacent the edge of the board against which the pivot point is placed. Next, the user typically marks the cut line along the marking edge of the side leg. Oftentimes, however, the distance across the board, along the angle at which the marking edge is placed, is greater than the length of the measurement edge itself. In these instances, the user may simply draw a partial line using the measurement edge, reposition the rafter square, to place the hypotenuse edge adjacent the partial line, and then complete the base cut mark. However, additional steps in the marking process become time consuming and cumbersome over the course of a framer's day. Moreover, repositioning the rafter square in order to make a second attempt at the base cut mark increases the risk that the resulting mark will be inaccurate. Until the present invention, however, the only alternative to this additional step was to guess at the exact position of the remainder of the partially drawn base cut mark by drawing the remainder of the mark freehand.
Accordingly, what is needed is a rafter square that functions similarly to prior art rafter squares until a cut mark is required that is longer than one or more of the edges found on a prior art rafter square, at which time the marking edge should be capable of being selectively extended across the remainder of the board. The design of such an improved rafter square should provide ease of use in extending and retracting the marking edge in order to reduce the overall time spent using the rafter square, relative to the time spent using prior art rafter squares.